During the operation of combustion engines the quality of the combustion events depends on various conditions. One condition is how well the fuel is mixed with air in the combustion chamber. A poor air fuel mix may yield unwanted soot, and/or hydrocarbon emissions. This may be, in particular, during cold starts.
Fuel injectors have been used to inject fuel into the combustion chambers of engines, typically at high velocity in an attempt to atomize the fuel. However, fuel injectors may still provide disappointing air fuel mixing. In addition, long spray penetration, often characteristic of the injectors, may result in the spray hitting the combustion chamber wall, which, especially in cold engine conditions, may tend to keep the fuel at a cooler, liquefied, state.
U.S. Pat. No. 7,458,364 to Allen discloses a fuel injection system wherein an attempt is made to improve atomization. The '364 disclosure includes a so called mixing chamber into which a positive displacement pump injects a measured amount of fuel. An air, or exhaust gas, conduit provides a gaseous make-up volume to the mixing chamber as a partial vacuum is produced in the adjacent combustion chamber to pull exhaust gas and fuel into the combustion chamber in a combined stream in an attempt to entrain the fuel into the exhaust stream. The vacuum is created in the combustion chamber by delaying the opening of an inlet valve as the piston starts a downward stroke. The mixing chamber includes an atomizing nozzle at an outlet side thereof, to accelerate the flow.
This approach has a number of shortcomings. For one, the '364 system requires a very particular operation of the charge air inlet valve in order to create a vacuum in the combustion chamber to cause air or exhaust to flow through the mixing chamber to entrain the fuel. The '364 design is intended to be used with smaller single cylinder engines that do not include a fuel pump. The positive displacement pump is designed for metered injection, not for increased pressure. In addition, there appears to be a relatively short time during which the fuel is exposed to the passing air or exhaust flow. There also appears to be little time for any appreciable heat transfer between the fuel and exhaust. The stream of exhaust and stream of fuel appear to be merely blended. It appears the fuel only becomes atomized as it passes from the atomizing nozzle into the combustion chamber within the blend.
The inventors herein disclose an engine, a fuel injector, and a method of injecting fuel into a combustion chamber of the engine that provides an improved air-fuel mixture. The method may include rotating an inner element relative an injector body a first rotational amount and aligning an exhaust gas passage with an exhaust gas source to allow exhaust gas to enter a pre-chamber for a first duration. The method may also include rotating the inner element relative the injector body a second rotational amount and aligning a fuel passage with a fuel source to allow fuel to enter the pre-chamber for a second duration. The method may also include rotating the inner element relative the injector body a third rotational amount and aligning injector nozzle connectors with injector nozzles, for a third duration, to allow a mixture of the fuel and the exhaust gas to be injected from the pre-chamber to the combustion chamber. Embodiments may provide a three-stage (exactly three-stages in one example) fuel injector configuration which introduces hot exhaust flow inside a pre-chamber inside the injector pin to promote fuel evaporation before being injected into combustion cylinder.
In this way, more significant exposure of fuel to warmed exhaust gas may be accomplished via a predetermined temporal exposure, and via sufficient spatial exposure. In this way, the fuel may be warmed in the prechamber. The fuel may be provided with sufficient heat transfer exposure with a supply of exhaust gas to effectively heat the fuel to advantageous levels. Also in this way, the fuel may be evaporated in the heated exhaust gas.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.